In providing valves and related elements for high-pressure environments the problems of rapid seal deterioration and high stem torque as a result of the high pressures are always encountered. This is particularly so in the valving of fluids at 20,000 psi, as is necessary in many modern fluid systems. Past attempts to solve such problems have not been entirely successful, often just relying on the quality of sealing materials, which have finite limits. U.S. Pat. No. 3,288,473 attempts to solve the problem of short seal life by providing a plurality of sealant passageways, each to be filled with sealant as the previous seal fails. This merely provides a temporary remedy, however, rather than solving the problem.
According to the present invention a long-life, low stem torque, valve stem seal is provided by utilizing a series of pressure barriers, each barrier withstanding only a fraction of the total pressure differential between the fluid cavity to be sealed and the atmosphere. Plastic is injected between each of the fluid elements of the barriers at a pressure that decreases from the high-pressure cavity to the atmosphere. Various means may be utilized for maintaining the plastic under the proper pressure in each chamber between barriers, such as a one-way pressurized injection valve, an exterior high-pressure chamber, or a channel having plastic under high-pressure with a plurality of differential back-pressure valves therein.
It is the primary object of he present invention to provide an improved apparatus and method for providing long-life shaft seals and low stem torque in high-pressure environments. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.